Remove willRequestResource callback, it is unused outside of tests.

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index 2fae09735592bb16a1dcc583577eb81d95dda419..88aecccbca3350ccb443c3ce93c2289520fb7320 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -355,8 +355,6 @@ ResourcePtr<Resource> ResourceFetcher::requestResource(FetchRequest& request, co
     if (!context().canRequest(factory.type(), request.resourceRequest(), url, request.options(), request.forPreload(), request.originRestriction()))
         return nullptr;
 
-    context().dispatchWillRequestResource(&request);
-
     if (!request.forPreload()) {
         V8DOMActivityLogger* activityLogger = nullptr;
         if (request.options().initiatorInfo.name == FetchInitiatorTypeNames::xmlhttprequest)